Researchers have developed a test that may soon allow doctors to track the progress of lung cancer tumors in “real time.” A sophisticated device allows doctors to detect and isolate the few circulating tumor cells that travel through the blood stream, which can then provide information about the main tumor’s growth and its response to medication.

As tumors grow, a handful of cancer cells may peel away and slip into the blood, [study author Daniel] Haber says. While few in number — with about one cancer cell for every 1 billion blood cells — these cells can be deadly if they settle in other parts of the body and form new tumors, a process called metastasis. Until now, doctors have never been able to easily analyze them [USA Today]. Now doctors will be able to conduct a genetic analysis of the free-floating tumor cells, allowing doctors to tailor their treatment to the individual patient and taking an important step towards “personalized medicine.”

Currently, doctors observe changes in a lung cancer tumor by conducting CT scans every six to eight weeks; by switching to the easier blood tests, doctors could get information about the tumor’s response to medication every week or two. In an additional advantage, doctors could easily check a circulating tumor cell’s genetics to see if the main tumor is likely to respond to certain drugs; currently doctors can only retrieve lung tumor cells by conducting invasive needle biopsies.

In the study, published in the New England Journal of Medicine, researchers describe their microchip scanner, which is the size of a business card. The tiny device has 78,000 posts imbedded inside to trap cancer cells. Each of those posts is coated with a substance that acts like glue – glue designed to stick only to circulating tumor cells…. “It’s like a pinball machine – the blood has to flow through all of these columns to get to the other side,” [said Haber]. “All the normal blood cells flow right through, but the very, very rare cancer cells stick to the columns” [The Boston Globe]. It will be several years before the chips appear in doctors’ offices, but Haber says that researchers may begin to use them in clinical drug trials very soon.